In increasingly complex reproduction or copier machines, customers demand an ever increasing amount of options, while at the same time demanding lower cost and greater reliability. This is particularly true in the low copy volume copier market, where most copiers are sold. Until recently, small size has been achieved by leaving out features commonly found in larger, more expensive machines. Now, customers regularly demand the same features in smaller sizes and at lower cost.
Of particular interest in smaller copiers is the provision of duplex copying. Duplex copying, i.e. copying onto both sides of a single copy sheet, is a desirable feature for the reduction of quantities of paper, and the production of attractively reproduced materials. It is often possible and desirable to copy two documents (originals) having images only on a single side (simplex documents) onto both side of a single copy sheet (duplex copy). This is sometimes accomplished in post collation machines (machines having an copy sheet output into sorter bins, or without recirculating document handlers) by making a desired number of first side copies in a reproduction processor, passing the first side copies to a duplex tray for temporary storage, and subsequently inverting and refeeding the first side copies to the reproduction processor to receive second side image information thereon. This function has also been accomplished by allowing two documents to be manually placed on a copying machine platen in side-by-side closely spaced relationship (two-up), and sequentially scanning each document to produce copies thereof. The first side copy sheets are inverted and returned immediately to the reproduction processor to receive second side copy thereon. Scanning of the documents to provide light images from each document on the platen, may be accomplished by either a scanning platen, as described in U.S. Pat. No. 4,017,173 to Komori, or with scanning optics as described in United States Patent Application Ser. No. 814,827. Also described are arrangements for the return of copy sheets bearing first side copy to receive second side copy thereon.
U.S. patent application Ser. No. 814,827 also describes a trayless path arrangement, which allows two documents, manually placed on the platen, each to be sequentially scanned twice, thereby passing two first side documents through the trayless path and back to the reproduction processor to receive second side copy thereon. It will be appreciated that the trayless paper path is significantly more reliable and somewhat faster than a path requiring refeeding from a duplex tray. Accordingly, it would be desirable to make maximum use of this capability by providing an automatic document feeder which provides both documents in appropriate position for scanning each sequentially.